I'll make a period tracker for you for 5 bucks a month. You won't buy it, because it costs 5 bucks a month. So I'll have to find alternative monetisation strategies.
Doesn't flo charge ten dollars a month?
https://help.flo.health/hc/en-us/articles/4411278780564-What...
Nobody is going to trust your $5 a month service.
why does it have to be 5 bucks a month and not a one time purchase?
there is a third option: don't make one at all if you feel your only recompense involves selling this data. that's what creeps do.
Why would me giving you 5 bucks a month assure you didn't also sell all of the data from the period tracker app? That's money you'd just be leaving on the table.